1. Field of the Invention
The present invention relates to an information processing apparatus, an information processing method, and a storage medium.
2. Description of the Related Art
Conventionally, there is machine learning technology for analyzing a new pattern with the use of learning patterns. Among them, a pattern recognition method (Leo Breiman, Jerome Friedman, Charles J. Stone, and R. A. Olshen, “Classification and Regression Trees,” Chapman & Hall/CRC, 1984) (hereinafter referred to as the non-patent document) called a classification tree or decision tree has been proposed, and adopted by many systems. This method is characterized by its ability for high-speed pattern analysis utilizing a tree structure, and demonstrated its ability in an age when calculators' performance was poor. Note that, when a pattern recognition problem is considered to be a pattern identification problem, the type of pattern to be identified will be referred to as a “class,” and in the following description, the term “class” will be used in this sense.
Meanwhile, a disadvantage of the classic classification tree or decision tree, which is suggested by the non-patent document, lies in the fact that recognition performance is not so good. To overcome this disadvantage, for instance, a method utilizing a group of classification trees (ensemble) as suggested by U.S. Pat. No. 6,009,199 has been proposed. In this method, L number of classification trees are created (L is a constant larger than or equal to 2, and is normally in the range of 10 to 100). With the use of all the classification trees, the method realizes higher recognition performance. This method has a disadvantage in that it requires L times as much calculation time as the conventional method utilizing one classification tree, thus sacrificing the characteristic of high-speed pattern recognition of the conventional classification tree. However, due to the recent improvement in calculators' performance, the method utilizing ensemble of classification trees has become feasible within a realistic time. Also, because of its high recognition performance, this method has recently been employed by many systems. Incidentally, although this method is slower than the algorithm of the classic classification tree, it achieves high-speed and equal-level performance of pattern recognition, compared to the pattern recognition method utilizing a support vector machine disclosed in Japanese Patent Laid-Open No. 2005-339186.
However, assuming a case of an application utilizing an image as a pattern, real-time pattern recognition is often required, and thus a higher-speed pattern recognition algorithm becomes necessary. Even in the method utilizing an ensemble of classification trees, which has been disclosed in U.S. Pat. No. 6,009,199, calculation time for recognition processing is not enough, and further improvement in speed is required.